The present invention relates to a method and a device for minimizing the amount of a fine powder sticking to the walls of a distribution member carrying a mix of air and the powder.
Within some technical areas there is a problem in that some part of a fine powder mixed with a gas and subsequently transported by this gas, e.g. air, will stick to the walls of a distribution member when it passes through this distribution member. Instruments for measuring for instance the amount of powder mixed with a transporting gas as well as providing a measure of the grain size distribution often faces the problem that the different sizes powder grains to be measured will easily stick to the walls of a measurement channel. This implies that cleaning must be regularly performed when measuring, besides the accuracy of the measurement will be very dependent of how often measures for cleaning will be performed.
Another area facing a similar problem, for instance, is the administering of medical compositions by means of inhalers. Administering of medical powders today can be performed in numerous ways. Within health care more and more is focussed on the possibility of dosing medical drugs as a powder directly to the lungs of a patient by means of an inhaler to thereby obtain an effective, quick and patient-friendly administering of such substances.
For the medical powders, being administered by means of an inhaler, to land in the lungs, the powder should preferably have a grain size of 0.5 to 10 xcexcm. A larger grain size will easily be sticking just in the mouth and throat, and a smaller grain size may accompany the expiration air out again.
Small grain size powder also has a strong tendency of agglomerating, i.e. to get conglomerated. In the inhalers, which are used today, a large extent of the active substance is in the form of agglomerates when it is dosed and much powder therefore will stick in the upper respiratory tract. Different ways to de-agglomerate the powder have been developed and in most cases the inhalation air is utilized for decomposing the agglomerates.
It is also common to use carriers having a larger grain size onto which the fine powder is distributed. Upon inspiration the large grains will then stick in the oral cavity while the small grains are set free and proceed to the lungs. Certain manufacturers also use electrically driven propellers, piezo-vibrators and/or mechanical vibration to decompose the agglomerates. Thus, achieving a very large portion of individual particles in the inspiratory air is a very important factor for obtaining a high degree of effectiveness upon inhalation. Yet another problem is that the medical composition powder also will stick to the walls of an inhaler distribution member normally connected to a suitable mouthpiece for the administration by means of an inspiration.
Therefore there is a demand of a solution which will to a large extent prevent particularly fine powder or its agglomerates from sticking to a distribution member, for instance, in a measuring instrument or an inhaler, which otherwise may be more or less clogged due to powder sticking to its walls.
A powder distribution device for transporting and mixing of a fine powder with a gas is disclosed. The device presents a distribution member forming a connection between a source of fine powder and a discharge opening. The distribution member has a first inlet portion and an outlet portion for a stream of a first gas mixed with the fine powder. The main body of the distribution member constitutes a porous body portion being surrounded by a second gas. If a pressure gradient is created between the second gas and the first gas, i.e. the first gas being at a slightly lower pressure, the second gas will leak trough the porous body and thereby preventing powder, in the mix of the first gas and fine powder, from sticking or clogging within the distribution member, which thereby obtains an active non-sticking wall relative to of the fine powder.
A method according the present invention is set forth by the independent claim 1 and the dependent claim 2. A device according to the invention is set fort by the independent claim 3, and further embodiments of the device are set forth by the dependent claims 4 to 9.